That's intriguing, could you provide a link? If all females can just reproduce more, I would expect one would break ranks and increase her own fitness by maxing out regardless.
I was also intriqued and put ~10min looking into it. This study[1] seems to suggest that although reproduction rates might increase modestly when the population is reduced, high immigration rates are the bigger factor. If anyone finds anything on the (voices disappearing)->(estrus) mechanism described above I'd like to see it, sounds really interesting.